Smart Mesoflaps for Aeroelastic Transpiration

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Smart Mesoflaps for Aeroelastic Transpiration

• Marina Tharayil
• Advisor Andrew Alleyne

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Overview

• Background
• What is SMAT concept?
• Earlier results, PC I
• Current Work
• PC II
• Results
• Future Work
• Whats next?

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Background

• Shock waves are generated in supersonic jet
  inlets.
• Cause flow seperation and unsteadiness (SBLI)
• The flow into the engine needs to be smoothed
  out.
• Currently, bleed systems are used - they have
  many disadvantages (add weight, space, etc.)

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Background SMAT Goal

• Smart Mesoflaps for Aeroelastic Transpiration.
• A matrix of flaps covering an enclosed cavity
• Mesoflaps locally deflect in cantellever mode,
  taking advantage of pressure differential on
  either side of shock incidence

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Background Control idea

• Input change flap deflection
• Output change downstream flow characteristics
  (stagnation pressure / boundary layer thickness)

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Background How to?

• How to change Flap deflection?
• Thermally Activated Smart Material (TASM) flaps -
  made of
• Change stiffness as a function of temperature

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Nitinol Material Properties

• Hysterisis
• Changes properties between the 2 states
• 40 GPa for martensite, 70 GPa for austenite

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Benchtop Tests (Pete)

• A single flap under pressure.
• Laser sensor for Deflection feedback
• Minco heater to heat the flap
• Insulation on flow side.

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Simulations Results

• PI controller
• Model hysteresis, thermal dynamics (1st order)

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Results

• Deflection with rate limit.

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Current Work - PC II

• Plenum Chamber II
• 15mm x 60mm Flaps, 0.005 thick.
• Can have upto 4 flaps (currently working with
  one)
• Pressure transducer, thermocouple and laser
  displacement sensor for measurements.
• Minco heater - 6.4mm x 58.4mm

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Plenum Chamber II
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Step Responses
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Step responses

• Rate limit increases as the power input is
  increased.
• Energy of phase transformation of SMA
• Qi Qjoule Qconvection Qtransformation
• Relation between transformation rate (dz/dt), net
  heat in, and z ( of Martensite)
• Model shows transformation rate changing very
  slowly for a fixed power in.

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Transformation model

• First order increase in temperature until
  transformation begins
• Maximum rate of transformation at Austinite Start
  Temperature.

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Step Responses - Model Vs. Exp.
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Control Model

• Simplified model
• Thermal Dynamics
• first order
• rate limited
• hysterisis - thermal dynamics to stiffness

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Future Tasks

• Control
• PI controller
• More suitable controller for system with rate
  limit.
• Pressure feed back
• Multiple flaps
• Wind tunnel experiments.

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Questions?